The proposed research will adapt and standardize for clinical use a direct, noninvasive method for measuring human iron stores by the in vivo determination of hepatic magnetic susceptibility. This safe, rapid and readily applicable technique can now detect iron overload in hemochromatosis, even in the precirrhotic stage, and make possible prevention of tissue damage by prophylactic phlebotomy; previously liver biopsy was required. Changes in iron stores may be monitored in patients being supported with transfusions (Thalassemia; aplastic anemia) or receiving treatment with iron chelators or phlebotomy. Finally, the hepatic magnetic susceptibility is a direct measure of a fundamental physical property of storage iron and will be free of the confounding influences which have limited the clinical usefulness of indirect estimates of human iron stores.